In blasting operations, initiation systems rely on an interconnected network of detonators, timing elements and the like. These elements are generally interconnected by flexible cords for transmitting signals between the various elements. In order to facilitate deployment of these flexible cords a variety of packaging systems have been used. For example, the so called"Figure of 8"winding has been employed in the packaging of initiation cords. Such winding configurations seek to provide tangle-free deployment of the flexible cord. A variety of variations on this configuration, such as have been described in Australian Patent Application No.

15097/92 (the so called"Figure 80"configuration), have been proposed. Generally these tangle-free winding configurations are produced by winding the flexible cord around two offset winding supports. The wound configuration of the flexible cord is then held in place by one or more frangible paper binders. The winding of cords about off-set winding supports generally requires the use of winding equipment which can perform complex movement in order to achieve an automated process. We have now found a process for winding a flexible cord in a comparatively tangle-free configuration on a drum or spool thereby providing improved efficiency in the cord winding process.

The present invention also provides a number of novel configurations of flexible initiating cord which are comparatively tangle-free.

According to the present invention these provided a coiled flexible initiating cord comprising a leading end and a coiled portion formed by a plurality of successive coils of the flexible initiating cord, wherein two or more of the successive coils are located on opposite sides of the leading end of the flexible initiating cord, and wherein said

coiled cord further comprises a coil retainer for holding the plurality of successive coils in a coiled configuration.

In a second aspect of the invention there is provided a process for producing a coiled flexible initiating cord, said process comprising the steps of: a) releasably engaging a leading end of the flexible initiating cord with a central portion of a winding support; b) winding a plurality of successive coils of the flexible initiating cord onto the winding support wherein two or more successive coils of the flexible initiating cord are wound on opposite sides of the leading end of the flexible initiating cord; and c) applying a coil retainer means to the coiled flexible initiating cord for holding the plurality of successive coils in a coiled configuration.

According to a third aspect of the present invention there is provided an apparatus for producing a coiled flexible initiating cord, said apparatus comprising a winding support, having means located in a central portion thereof for releasably engaging a leading end of the flexible initiating cord, said apparatus further comprising a means for winding a plurality of successive coils of the flexible initiating cord relatively around the winding support such that two or more of the successive coils of the flexible initiating cord are wound on opposite sides of the leading end of the flexible initiating cord and said winding apparatus further comprising means for applying a coil retainer means for holding the plurality of successive coils in coiled configuration.

A wide variety of flexible initiating cords for use in the initiation of explosives may be wound in accordance with the present invention. For example, the present invention may be used to wind electrical initiating cord, detonating cord, igniter cord, non-electric shock tube, hybrid cords and the like. The present invention is particularly suited to the winding of the non-electric shock tube.

Explosive initiation systems incorporate a plurality of detonators interconnected via a network of flexible initiation cords. The initiation cords may be interconnected by a variety of connector means. Generally the flexible initiation cords are provided with connectors and/or detonators affixed thereto. Flexible initiation cords generally are provided in three configurations. The first configuration comprises a detonator affixed to one end and a connector, of the"J-hook"type at the other. A second configuration comprises a detonator at both ends, with one of these detonators located within a connector block. The third configuration comprises a connector, such as of the"J- hook"type at one end and a detonator encased in a connector block at the other.

In the present invention two or more successive coils of the flexible initiating cord are located on the opposite sides of the leading end of the flexible initiating cord. It is preferred that 3 or more successive coils are located on alternating sides of the leading end, more preferably 4 or more successive coils are located on alternating sides of the leading end. In the most preferred winding configuration all of the plurality of successive coils are located on the alternating sides of the leading end of the flexible initiating cord. However, it is not essential to the present invention that every successive coil is located on the alternating sides of the leading end and it is possible that the coil of flexible initiating cord comprises two successive coils on one side of the leading end of the flexible initiating cord followed by a further two successive coils on the other side. Various modifications and variations of the winding scheme will be acceptable. For example, we have found that six successive coils on one side of the leading end prior to alternating to the other side will still give acceptable, tangle free deployment.

It is preferred that in the coil of flexible initiating cord there be an equal number of coils located on respective sides of the leading end of the flexible initiating cord.

The coil of flexible initiating cord may be packaged by a coil retainer such as generic taping (paper taping) of the type currently used for retaining coiled non-electric shock tube. Alternatively the coil of flexible initiating cord may be packaged using shrink-

wrap packaging or a band covering the central portion of the coil.

A wide variety of winding supports may be used in the present invention. Winding supports may be in the form of winding frames comprising 2 or more members, although it is preferred that the winding support for use in the present invention is in the form of a spool, reel, spindle or the like. For convenience such winding supports will be referred to herein generically by the term"spool".

The winding support must be constructed such that the wound cord may be removed from the winding support, such as for packaging and/or distribution. In one embodiment, the winding support may be provided with a removable flange such that the coiled cord may be disengaged from the winding support in a coiled configuration.

Preferably the winding support comprises a fastening means for holding the leading end of the flexible initiating cord. The fastening means is located such that windings of the flexible initiating cord may be accommodated on either side of the leading end of the flexible initiating cord. The preferred fastening means is a channel provided with overhanging tabs to releasably engage the flexible initiating cord.

In a preferred embodiment of the invention the winding support is a bifurcated spool.

Preferably the bifurcated spool is divided in a central portion thereof and the leading edge of the flexible initiating cord is releasably engaged with the winding support by moving two parts of the bifurcated spool relatively towards each other.

The flexible initiating cord may be wound around the spool by either rotating the spool or by circulating a reel of flexible initiating cord about the spool.

The coil of flexible initiating cord may be removed from the spool for packaging by any convenient means. In a preferred embodiment of the present invention the winding support is provided with a longitudinal channel such that a tape or gripping means may be passed therethrough and under the coiled cord whereby the cord may be taped in situ or gripped for removal from the spool.

Coiled non-electric shock tube produced according to the present invention may be affixed to detonators, connector blocks and/or connectors such as J-hooks and the like.

The flexible initiating cord may be deployed in a comparatively tangle free manner by uncoiling the coil of flexible cord from the leading end of flexible initiating cord. By withdrawing the leading end of the flexible initiating cord, the successive coils adjacent to, and alternating on either side of, the leading end may be successively deployed.

The present invention will now be further described with reference to the non-limiting drawings.

Figures 1 to 5 illustrate a preferred winding arrangement according to the present invention.

Figure 6 is a cross-section of a spool wound in accordance with the present invention.

Figure 7 is a perspective diagram of a spool wound in accordance with the present invention.

Figure 8 is a perspective diagram of one segment of a bi-partied spool in accordance with the present invention.

Figure 1 shows the beginning of the flexible initiating cord (1) has a leading end (2).

Figure 2 shows the winding advanced approximately one revolution. The initiating cord (1) can be seen to pass over the leading end (2) at intersection (3). The winding passes underneath the leading end (2) at intersection (4). Figure 3 shows the winding advanced a further revolution. The flexible initiating cord (1) passes under the leading end (2) at intersection (5) and over the leading end (2) at intersection (6). Figure 4 shows the winding advanced a further revolution. The flexible initiating cord (1) passes over the leading end (2) at intersection (7) and under the leading end (2) at intersection (8). Figure (5) shows the winding advanced a further revolution. The flexible initiating cord (1) passes under the leading end (2) at intersection (9) and over the leading end of the flexible cord at intersection (10). The preferred embodiment of the present

invention represented in figures 1 to 5 may be continued with subsequent revolution alternating between either side of leading end of the flexible cord (2).

Figure 6 shows the spool (11) having a channel (12) through which the leading end (2) of the flexible initiating cord (1) is passed. The windings (13) are wound in an alternating manner on either side of the leading end (2). The windings are wound about the drum portion (19) of the spool (11). A flange (18) retains the windings (13).

Figure 7 shows the spool (11) having the flexible initiating cord (1) wound thereon. The flexible initiating cord (1) is wound alternately about the leading end (2) of the flexible initiating cord (1). The flanges of the spool (18) have a channel (14) therein.

The channel (14) extends below the surface of the drum portion (not shown) and extends longitudinally along the drum portion to provide a channel (15) below the windings (13). The channel (15) allows the windings (13) to be conveniently gripped and/or taped for packaging.

Figure 8 shows one section of a bifurcated spool (16). The second element (not shown) may be a mirror image of the first element (16) or may be any other convenient configuration. The first element of the bifurcated spool has a flange (18) for retaining the windings (not shown) on the surface of the drum (19). The inner end (20) of the first element (16) has a channel (17) for receiving the flexible cord (not shown). The second element of the bi-partite spool may engage the first to provide an interference fit for the flexible cord (not shown) in the channel (17) with an opposing channel in the second element (not shown).

Throughout this specification and the claims which follow, unless the context requires otherwise, the word"comprise", and variations such as"comprises"and"comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

Those skilled in the art will appreciate that the invention described herein is susceptible

to variations and modifications other than those specifically described. It is to be understood that the invention includes all such variations and modifications which fall within its spirit and scope. The invention also includes all of the steps, features, compositions and compounds referred to or indicated in this specification, individually or collectively, and any and all combinations of any two or more of said steps or features.